Blasting machine



June 30, 1953 R. A. SCHMITT ETAL 2,644,117

BLASTING MACHINE Filed July 2, 1952 INVENTORS R T A. SCHMITT BY flfl dATTORNEYS Patentecl June 30, 1953 UNITED STATES PATENT GFFEQE 2,644,117BLAS'IING MACHINE Application July 2,1952, Serial No. 296,872

The present invention relates'to a blasting machine. More particularly,the present invention relates to a blasting machine for use with a non--explosive blasting cartridge of the pressure-reslstant tube type whereinthe gas-producing charge consists of a chemical composition which isinitiated by the application of heat.

In co-pending application Serial Number 174,818, filed July 20, 1950, byDavis, Glogau, Loving, and Swed, a blasting assembly is describedwherein a reusable pressure-resistant tube contains a prepackaged chargeof ammonium nitrate sition, and that the current must be sustained forseveral seconds. The burning through of the ribbon interrupts thecurrent, thus reducing the likelihood of sparks occurring outside of theblasting cartridge.

It is an object of the present invention to provide a device for thesafe initiation of the blasting cartridges described above. A furtherobject is to provide a portable controller for the safe application ofcurrent to initiate a blasting cartridge. Additional objects will becomeapparent as the invention is further described.

We have found that the foregoing objects may be attained when we providea blasting controller adapted to provide a current of from '2 to 11amperes as long as the starter ribbon is effective, and then todiscontinue the current to the blasting cartridge.

In order to more fully describe the present invention, reference is madeto the accompanying drawing which represents a diagram of a circuitadapted to produce the desired results.

In the drawings, l is a power source, for example, a 36 volt wet storagebattery, 2 is a fuse, e. g., 20 amperes, 3 is a snap-toggle typedouble-pole switch and 4 is a dual-coil current regulating relay adaptedto be energized by a current in excess of 13 amperes, mechanicallylatching in the energized position, and electrically resetting by thesecond coil. 5 is a set of breaker points actuated by relay 4 and B is apushbutton switch 5Claims. ((21. 31780) in series with the resettingcoil of relay 4. l is a condenser, preferably an electrolytic type, 8 isa snap-toggle double throw switch'which connects the condenser I'circuit'to either contact 9 or contact ID. i! is a dual coil relay, onecoil in series with the condenser circuit adapted to energize the relaymomentarily, and a second coil in series with the firing circuit adaptedto maintain the relay in the actuated position while a current of atleast 2 amperes fiows therethrough. l2 and I3 are breaker pointsactuated by relay i I. I4 is a resistance element, [5 is an indicatorlight, and I6 is an outlet receptacle.

In operation, one or more blasting cartridges are connected to thepresent device at receptacle 1 6. Main line switch 3 is then closed, andpushbutton 6 depressed to insure the closing of points 5 by relay 4.Snap-toggle switch 8 is thrown to connect with contact 9, thuscompleting the circuit from the power source l to the condenser 1, thelatter being charged thereby. When switch 8 is reversed, i. e.,connected with contact [8, the condenser T discharges through relay H,which is thus momentarily actuated, thereby closing breaker points [2and [3. This completes a circuit from power source I through relay H toreceptacle [6, and if at least 2 amperes current is flowing, relay llremains actuated, and the blasting cartridge starter ribbons receive therequired electrical current. As soon as the starter ribbon is burnedthrough, the current is interrupted and relay II is deenergized, thusopening the circuit. In the event a short occurs so that the currentexceeds 13 amperes, relay 4 is energized, thereby opening the circuit.Indicator light I5 will permit the operator to visually check whetherthe circuit was completed and continued for a sufficient length of timefor the initiation of the charge.

The essential features of the present invention reside in a relay inseries with a firing circuit to disconnect the power source from thelead wires as soon as the starter ribbon is parted, the use of acondenser circuit to momentarily energize the relay to provide a closedfiring circuit, and relay means for limiting the current to apredetermined maximum value. Preferably, the device also contains anindicator light to visually apprise the operator of the operation of thefiring circuit, and a means for electrically resetting the currentlimiting relay in the event it has become energized. The fuse is presentmerely to protect the assembly in the event of a short circuit. It mayalso be desirable to connect an ammeter in series with the firingcircuit so that the operarent value between 2 and 11 amperes isdeliverable to the blasting cartridge.

While the invention has been fully described with reference to thespecific'embodiment illustrated in the drawing, it will be understoodthat variations in design and construction may be 7 made withoutdeparture from the spirit of the invention. Therefore, we intend to belimited only by the following claims:

We claim:

1. A blasting machine comprising a firing circuit, means for connectingsaid firing circuit toa source of electrical energy, a condenser circuitcontaining a condensena dual coil relay having one coil in series withsaid firing circuit adjusted to maintain said relay in an energizedcondition when a current of a predetermined magnitude flows in saidfiring circuit, and a second coil adjusted to momentarily actuate saidrelay from the energy of a condenser discharge, switch'me'ans which inone position connects the condenser circuit in parallel with the firingcircuit and in the second position in series with the second coil ofsaid relay, circuit closing elements connected in series with saidfiring circuit and actuated by said relay, and electrical means foropening said firing circuit if the current exceeds a pre determinedmagnitude.

2. A blasting machine comprising a firing circuit, a battery, manualswitch means for connecting said battery with said firing circuit, acondenser circuit containing a condenser, a dualcoil relay having onecoil in series with said firing 4 1 mined'magnitude flows therethroughand a second coil adjusted to momentarily actuate said relay from theenergy of a condenser charge, switch means which in one positionconnects the said condenser circuit in series with said battery andin'the'secondposition in'serie's with said second coil of said relay,circuit closing elements connected in series with said firing circuitand actuated by said relay, and electrical means for opening said firingcircuit if the current exceeds a predetermined magnitude.

- 3. A blasting machine comprising a firing circuit, a battery, switchmeans for connecting said battery in series with said firing circuit, acondenser circuit containing a condenser, a dual coil relay having onecoil in series with said firing circuit adjusted to maintain said relayin an energized condition when a current of predetermined magnitudeflows therethrough, and a second coil adjusted to momentarily actuatesaid relay from the energy of a condenser discharge,

"switch means which in one position connects the condenser circuit inseries with-said battery, and in the second position in series with saidsecond coil of said relay; circuit closing elements con nected in serieswith said firing'circuit and actu' ated by said relay, and a secondrelay having a coil in series with said firing circuit adjusted toenergize said relay at a predetermined current higher in magnitude thanthat required to maintain the first relay in an energized condition,said second relay actuating circuit-breaking elements connected inseries with said firing circuit.

circuit adjusted to maintain saidrelay in an 4. A blasting machine asclaimed'in claim 3, wherein the first relay will be maintained in-anenergized condition by a current of at least 2' amperes, and said secondrelay will be energized by a current in excess of 13 amperes.

5. A blasting machine as claimed in claim 3, wherein said second relayis of the mechanically latching, electrically resetting'type.

ROBERT A. SGHMITT. JAMES P.-SWED. CHARLES =P. WILLIAMS.

N 0 references cited.

